Xerographic plate holder



Nov. 25, 1952 R, MA'YQ 2,619,418

XEROGRAPHIYC PLATE HOLDER Filed Dec. 30, 1950 INVENTOR CLYDES MAYO ATTORNEYS Patented Nov. 25, 1952 XEROGRAPHIC PLATE HOLDER Clyde R. Mayo, Rochester, N. Y., assignor to The Haloid Company, tion of New York Rochester, N. Y., a corpora- Application December 30, 1950, Serial No. 203,619

3 Claims.

This invention relates in general to xerography, and in particular to a xerographic or electrophotographic member suitable for easy and convenient use in xerographic processes.

In Carlson U. S. Patent No. 2,297,691 there is disclosed a process of electrophotography which has now become known as xerography. The basic member for this process is an electrophotographic plate comprising a conductive backing member having a photoconductive insulating layer or coating on one surface. This electrophotographic member is sensitized by applying an electrostatic charge to the photoconductive insulating coating, and the sensitized member is then exposed to a light image. Under the influence of the light the photoconductive insulating material becomes electrically conductive permitting the electrostatic charge to be selectively dissipated in the portions which are illuminated. In thi manner an electrostatic latent image is formed, corresponding to the dark portions of the image, and the latent image may then be developed with an electroscopic material which clings to the electrically-charged portions of the latent image.

This process originally disclosed by Carlson has more recently been developed and improved toward commercial application, one of the forms of application being reproduction and copying of letters, manuscripts and other documents. In this field it is possible to use as the photographic or xerographic plate a rigid metallic backing plate, such as a sheet of aluminum or other metal having on one face thereof a coating or layer of selenium in its vitreous or photoconductive insulating form.

To a certain extent the metallic plate and the vitreous selenium are physically incompatible and the incompatibility is further emphasized by preferred methods, procedures and equipment for operation of the xerographic process. For example, a metal sheet is generally characterized by being relatively flexible, whereas the vitreous selenium coating is very much like glass which it resembles in appearance and is characterized by being quite brittle and inflexible. Thus, extreme care must be taken to prevent the metal sheet from normal bending and buckling in use and operation, since such bending will cause the selenium coating to crack and chip off. This incompatibility of plate and coating becomes even more vexing because of a seemingly minor characteristic of preferred xerographic processes and developers. A presently preferred development process employed in the field of document copying contemplates cascading across the surface of an exposed plate a developer composition comprising a mixture of extremely small developer or toner particles and relatively larger carrier particles. The intent in this step is to have the toner particles cling to the carrier particles and thus be borne across the surface of the plate, and to have these toner particles be given up by the carrier to the selectively-charged portion of the xerographic plate. In actual practice, however, one side effect of this step is for the carrier particles themselves to adhere somewhat loosely to the plate, and a frequent possibility is for the carrier particles to adhere temporarily to the plate and later be deposited elsewhere in the mechanism. One result of this effect is that one or several carrier particles may eventually find their way between the xerographic plate and whatever mechanism is employed to hold documents or other copy in contact with the plate during exposure. As is readily apparent, this can and often does cause the metal plate to be bent, thus chipping or cracking the selenium coating.

Now, in accordance with this invention, there is provided a xerographic or electrophotographic member comprising a vitreous selenium-coated conductive plate of size suitable for documentary copying, the plate having a surrounding frame adapted to fit in for xerographic processes and simultaneously avoiding diificulties prevalent in presently preferred xerographic techniques. It is, therefore, an object of the invention to provide a new combination electrophotographic plate member. More specifically, it is an object of the invention to provide a new electrophotographic plate member of increased resistance to damage both from accidental mishandling and from xerography process operations. Other objects of the invention will be apparent from the description and from the drawings in which:

Figure 1 is an isometric view of a xerographic member according to one embodiment of the invention;

Figure 2 is a fragmentary enlarged cross section of the article shown in Figure 1 taken along line 2-2;

Figure 3 is a fragmentary enlarged cross section of the article in Figure 1 taken along the line 33; and

Figure 4 is a fragmentary enlarged cross section taken along line 4-4.

Figure 5 is a fragmentary enlarged cross section taken along line 55, showing operation of one feature of the member.

Referring to the figures in detail, there is shown a xerographic member generally desi nated l comprising an electrophotographic plate ll surrounded by and engaging a rigid frame l2 which surrounds and protects the four side of the plate. According to the preferred embodiment of the invention, this frame is light tight and is further provided with a light shield I3 slidably mounted in the frame by means of rooves l4.

As shown in Figure 2, the xerographic plate ll consists of a metal backing plate l5 having on at least one of its surface a coating or layer l6 of an insulating photoconductive or vitreous form of selenium. This selenium layer terminates short of the edge of the plate and provides a bare metal or non-sensitized border for the plate which is partially inserted in and engaged by the side of the frame i2. Spaced and removed from the selenium-coated surface of the plate is the light shield l3 which is adapted to slide into shield in position in grooves l4.

In Figure 3 is shown the construction of the 7 back end of the frame where there is an end frame member ll which is somewhat lower than the side frame members and which receives and engages the end of the metal plate 15. At the upper surface of the end frame member l1 and across the ends of grooves I4 is a shoulder or abutment is which is positioned and adapted to form a light seal with the light shield I3 when the shield is fully inserted in grooves M. This shoulder is preferably positioned at a place removed from the inner edge of the end frame member I? so that the light shield may be inserted for a substantial distance across the upper surface of the end frame member I7 and optionally contacting the upper surface, abutting against shoulder 18 and thus assuring substantially complete protection from the plate when the shield is fully closed.

In Figure 4 is shown the opposite or front frame member 19 which receives and engages the metallic sheet [5 and which is provided with a slot 20 communicating with the grooves M to receive and admit the light shield l5 whereby the light shield may be inserted through the slot and carried by the grooves to form a light-tight closure for the frame.

Figure 5 illustrates the action of a carrier particle 23 rolling along the surface of plate l5 in the path indicated by the dotted line, striking shoulder 2| and bouncing beyond groove [4 and thence oil the electrophotographic member.

In use and operation the xerographic memberis adapted to be employed in combination with many desired Xerographic charging, exposing and developing apparatus and the like. In the step of charging or sensitizing this xerographic plate it "is frequently advisable to employ a charging member consisting of a corona electrode (not shown) which is adapted to be passed across an area closely adjacent and parallel to the plate to be sensitized. In usual operation it is desirable to have this corona electrode pass as close to the surface of the plate as can be accomplished with reasonable allowance for tolerance of design and the like. Since it is preferred for obvious reasons to have the electrophotographic member adapted for insertion into a light-sealed slot for charging, it can reasonably be expected that the back frame member ii of the xerogr'aphic plate assembly will be required to pass beneath a closely adjacent corona electrode. Accordingly, the height of this member i! above the surface of the plate II should be as small as is consistent with other features of design. At the same time it is recognized that light shield l3 in use and operation is subject to a small degree of bending anddeforming which requires a substantial space between th light shield and the plate and thus requires a substantial elevation of shoulder [8 above the plane of plate H. In actual use and operation it has been found that a spacing between about es and about inch, and preferably about A; inch, is desired between plate II and the closely adjacent grooves I4 with its communicating slot 20 and abutment shoulder I8.

According to a preferred development technique and method, a latent electrostatic image on the xerographic plate may be transformed into a powder image by cascading across the surface of the plate a powder carrier mixture consisting of small-sized developer or toner particles supported and carried by large-size carrier particles. A difficulty which must be overcome is the tendency of these larger carrier particles to adhere loosely and temporarily to the plate either by virtue of electrostatic attraction or by virtue of mechanical adhesion. An end result of such temporary sticking of the carrier particles is that a carrier particle may adhere to the plate for a short time and then roll across the plate striking the edge of the frame. If this rolling occurs at a time when the light shield is removed from the frame, as is most probable since the powder is applied while the shield is removed, it is essential to provide some means to prevent the particle from lodging itself within grooves 14 from which position of lodgment it can later be moved to come between the plate l5 and whatever mechanism may be provided to insure firm contact between the plate and contact copy material. According to a preferred embodiment of the invention as illustrated in Figure '2, the inner surface of the frame member I2 is not uniformly spaced from the center of the frame but, instead, a lower shoulder 21 beneath groove l4 extends substantially further toward the center than does the upper shoulder 22. In this manner a rolling car rier particle strikes this lower shoulder and in bouncing is directed away from the opening of the groove as shown in and previously described for Figure 5.

As a result of this new combination electrophotographic member, xerographic copying can be carried out in convenient processing steps with a minimum of wear and damage to the delicate light-sensitive surface.

What is claimed is:-

l. An electrophotographic member of improved resistance to damage comprising an electrophotographic plate having a sheet metallic backing and a vitreous selenium coating thereon and a frame engaging and surrounding said plate, a slot at one end of the frame andcommunica-ting grooves to receive a light shield through said slot above the selenium coated surface of the plate, a rear frame member at the end opposite theslot to re ceive in abutment the end of the. shield when fully inserted through the slot, the inside faces of the side frame member having shoulders between the plate and the grooves and adjacent to the plate, extending further inwardly than the faces above the grooves whereby particles striking said shoulders are directed away from the openings of the groove.

2. An electrophotographic member of improved resistance to damage comprising an elec trophotographic plate having a sheet metallic backing and a vitreous selenium coating thereon and a frame engaging and surrounding said plate, a slot at one end of the frame and communicating grooves to receive a light shield through said slot above the selenium coated surface of the plate, a rear frame member at the end opposit the slot to receive in abutment the end of the shield when fully inserted through the slot, the inside faces of the side frame members having shoulders, between the plate and the grooves and adjacent to the plate, extending further inwardly than the faces above the grooves, whereby particles striking said shoulders are directed away from the openings of the grooves, and the rear frame member having its upper surface below the upper boundary of the grooves and having an abutment shoulder extending upwardly therefrom at a point removed from the inner wall thereof, whereby th light shield is adapted to pass over a substantial portion of the rearframe member and abut against the shoulder, thus forming a light seal with the frame.

3. An electrophotographic member of improved resistance to damage comprising an electrophotographic plate and a frame engaging and surrounding said plate, a slot at one end of the fram and communicating grooves to receive a 6 light shield through said slot above the electrophotographically-sensitive surface of the plate, a rear frame member at the end opposite the slot to receive in abutment the end of the shield when fully inserted through the slot, the insid faces of the side frame member having shoulders, between the plate and the grooves, extending further inwardly than the faces above the grooves, whereby particles striking said shoulders are directed away from the openings of the grooves.

CLYDE R. MAYO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 725,898 Walburn Apr. 21, 1903 1,109,873 Schoen Sept. 8, 1914 1,134,540 Kress Apr. 6, 1915 1,788,905 Barnes Jan. 13, 1931 2,277,013 Carlson Mar. 7, 1942 2,588,675 Walkup et al Mar. 11, 1952 

1. AN ELECTROPHOTOGRAPHIC MEMBER OF IMPROVED RESISTANCE TO DAMAGE COMPRISING AN ELECTROPHOTOGRAPHIC PLATE HAVING A SHEET METALLIC BACKING AND A VITREOUS SELENIUM COATING THEREON AND A FRAME ENGAGING AND SURROUNDING SAID PLATE, A SLOT AT ONE END OF THE FRAME AND COMMUNICATING GROOVES TO RECEIVE A LIGHT SHEILD THROUGH SAID SLOT ABOVE THE SELENIUM COATED SURFACE OF THE PLATE, A REAR FRAME MEMBER AT THE END OPPOSITE THE SLOT TO RECEIVE IN ABUTMENT THE END OF THE SHIELD WHEN FULLY INSERTED THROUGH THE SLOT, THE INSIDE FACES OF THE SIDE FRAME MEMBER HAVING SHOULDERS BETWEEN THE PLATE AND THE GROOVES AND ADJACENT TO THE PLATE, EXTENDING FURTHER INWARDLY THAN THE FACES ABOVE THE GROOVES, WHEREBY PARTICLES STRIKING SAID SHOULDERS ARE DIRECTED AWAY FROM THE OPENINGS OF THE GROOVE. 